Johnstone has been in superb form this season having kept 11 clean sheets as Steve Bruce's side push for an automatic promotion place.
"He will be with us, hopefully we go up then he will be permanently," Xia said on Twitter. "I think Villa is his fortunate place."
Johnstone spent the second half of last season on loan at Villa Park and kept 8 clean sheets in 22 appearances.
With David De Gea expected to remain at Old Trafford, the 24-year-old could be allowed the leave the Red Devils on a permanent basis.